TITLE: GCN CIRCULAR NUMBER: 20451 SUBJECT: GRB 170112A: Swift/UVOT Upper Limits DATE: 17/01/13 16:17:42 GMT FROM: Mike Siegel at PSU/Swift MOC M. H. Siegel (PSU) and B. Mingo (U. Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 170112A 279 s after the BAT trigger (Mingo et al., GCN Circ. 20436). No optical afterglow consistent with the BAT position (Lien et al., GCN Circ. 20443) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 856 1006 147 >20.5 u_FC 279 529 246 >19.9 white 856 6361 344 >21.0 v 5136 6771 393 >19.2 b 5956 6156 197 >20.0 u 279 7338 593 >20.4 w1 5546 7180 393 >19.9 m2 5341 6975 393 >20.2 w2 6366 6566 197 >20.0 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.02 in the direction of the burst (Schlegel et al. 1998).